After casing is cemented in a wellbore and any residual cement is cleaned out, operations are commonly performed to perforate the casing to establish fluid communication with the surrounding formation for fracture operations and eventual production. Various types of perforating equipment can be used to perforate the casing.
Wireline conveyed perforating equipment is one type of equipment used for perforating casing. For example, FIG. 1A illustrates a through-casing perforating gun 20 deployed in a wellbore 10 with wireline 24 from a wireline truck 26. The gun 20 has shaped charges 22 that produce perforations 14 in the casing 12 of the wellbore 10.
As another example, FIG. 1B illustrates a through-tubing perforating gun 30 deployed in a wellbore 10 with wireline 34 from a wireline truck 26. The gun 30 has shaped charges 32 that produce perforations 14 in the casing 12 of the wellbore 10. The charges 32 are exposed in the wellbore 10, and magnets can hold the gun 30 against the casing 12.
Tubing Conveyed Perforating (TCP) equipment is another type of equipment used for perforating casing. In this form of perforating operation, the TCP equipment consisting of one to ten guns is conveyed downhole to prepare the wellbore casing with perforations. The TCP equipment, which is nonelectric, then establishes the perforations in the casing and can be conveyed on coil tubing or on pipe.
For example, FIG. 1C illustrates a tubing-conveyed perforating (TCP) gun 40 deployed on a workstring 44, such as coiled tubing or jointed pipe, from a rig 46. The guns 42 are encapsulated in a housing, which can have flow entry ports 45 adjacent a firing head.
In the pipe-conveyed operation, multiple pressure-activated firing heads of the TCP gun 40 can be fired at the same time and may or may not have time delays attached. Pipe tally for the pipe 44 is used to correlate the position of the TCP equipment downhole in the casing 12, and a packer may or may not be run to isolate the annulus.
In the coil tubing-conveyed operation, one pressure-activated firing head or ball-drop-differential firing head fires first in the TCP equipment. Then, time delays between gun activations can allow the coil tubing 44 to move the TCP equipment to different zones to be perforated. In the end, the number of charges 42 that can be run and the different zones that can be perforated may be limited by the equipment at surface. A depth recorded from a clean-out run with the coil tubing 44 can be used to correlate the position of the TCP equipment downhole to the zones to be perforated.
As shown, the guns for perforating equipment come in two basic forms, exposed guns 30 as in FIG. 1B and hollow carrier guns 20, 40 as in FIGS. 1A and 1C. The exposed gun 30 is run on wireline and has its shaped charges 32 individually mounted on a strip, in a tube, or on a wire. The detonator and detonating cord for the charges 32 are exposed in the wellbore 10 to surrounding fluids.
For operation, the wireline system of FIG. 1B uses an electrical firing mechanism to initiate the firing process for the gun 30. In this process, an electrical initiation is communicated through the wireline 34 to the gun 30 to initiate the firing. In some operations, exposed energetic products cannot or are difficult to deploy on electric wireline. Yet, in some instances, exposed energetic products may still be useful.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.